The present disclosure relates generally to the field of terrain avoidance systems. More specifically, the disclosure relates to a terrain avoidance system that utilizes data base information to aid the transmit and/or receiver processing of the radar information to enable distinguishing between terrain, obstacles, and weather.
Terrain awareness systems (TAS), such as Terrain Awareness Warning Systems (TAWS), typically provide flight crews with information (e.g., alerts, warnings, displays of terrain data, etc.) related to detection of potentially hazardous terrain situations that pose or may pose a threat to continued safe flight and landing of an aircraft and provide warnings or alerts in sufficient time for the flight crew to take effective action to prevent a controlled flight into terrain (CFIT). Terrain awareness systems generally have three alerting functions including a Ground Proximity Warning System (GPWS) alerting function, a Forward Looking Terrain Avoidance (FLTA) alerting function, and a Premature Descent Alerting (PDA) function.
Terrain awareness systems have been implemented using terrain elevation databases to support the FLTA alerting function. These systems look ahead of the aircraft's current position by utilizing a terrain elevation database to determine if there is terrain in regions that would be potentially hazardous to the aircraft.
While not required by the FAA TAWS Technical Standard Order, alerting for obstacles (e.g., man-made structures like towers and buildings) that pose a hazard to the aircraft is often included in TAWS packages. Current TAWS packages tend to solely use obstacle databases to support this additional obstacle alerting function.
An alternative means of compliance with the FAA TAWS forward looking terrain alerting function requirements (which are currently defined in FAA Technical Standard Order (TSO) C115b) is a Radar-based TAWS (R-TAWS). Such a system uses airborne radar sensors (e.g., similar to the radar that is used for weather and windshear detection) to detect terrain and/or obstacles that are potentially hazardous to the aircraft rather than or in addition to using a database. However, this alternative method of detection that uses radar to detect terrain and/or obstacles in regions that may be hazardous to the aircraft may have difficulty achieving an acceptably low false detection rate.
An issue with this alternate means of compliance is distinguishing the difference between terrain, obstacles and weather in the region of interest. What is needed is a means to help distinguish between radar returns of terrain, obstacles and weather such that appropriate information can be used as part of an R-TAWS caution, warning, and alerting strategy for terrain and/or obstacles, as well as a weather and windshear hazard detection strategy.